// JavaScript Document
(function flexible(window, document) {
    var docEl = document.documentElement;     //获取文档根节点并保存到变量docEl中(相当于获取到html对象)
    var dpr = window.devicePixelRatio || 1;   //获取像素比，如果window.devicePixelRatio为false是dpr为1，如果window.devicePixelRatio大于1，那么dpr赋值取大的数

    function setBodyFontSize() {
        if (document.body) { 
            document.body.style.fontSize = (12 * dpr) + 'px';
        }
        else {
            document.addEventListener('DOMContentLoaded', setBodyFontSize);
        }
    }
    setBodyFontSize();

    // set 1rem = viewWidth / 10
    function setRemUnit() {
        var rem = docEl.clientWidth / 10
        docEl.style.fontSize = rem + 'px'
    }

    setRemUnit()

    window.addEventListener('resize', setRemUnit)
    window.addEventListener('pageshow', function (e) {
        if (e.persisted) {
            setRemUnit()
        }
    })

    // detect 0.5px supports
    if (dpr >= 2) {
        var fakeBody = document.createElement('body')
        var testElement = document.createElement('div')
        testElement.style.border = '.5px solid transparent'
        fakeBody.appendChild(testElement)
        docEl.appendChild(fakeBody)
        if (testElement.offsetHeight === 1) {
            docEl.classList.add('hairlines')
        }
        docEl.removeChild(fakeBody)
    }
}(window, document))
